<!DOCTYPE html>
<html lang="en">

<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
  <style>
    h1 {
      /* 彻底干掉一个元素 */
      /* display: none; */
      /* 位置在，内容不显示 */
      /* visibility: hidden; */
      /* !important会将优先级提到最高 */
      color: blue !important;
    }

    .hello {
      /* 选择器优先级: ice原则 i=id c=class e=element  
        所以优先使用id选择器的内容
      */
      color: red;

      /* 外边距可以使用负值 */
      margin-top: -30px;
    }
  </style>
</head>

<body>
  <h1 class="hello">Hello World</h1>
  <p>
    Lorem ipsum dolor sit amet consectetur adipisicing elit.
    Ea tempore quibusdam ipsa porro sit labore ipsam veritatis facilis a fuga placeat sunt tenetur sequi, officiis quia.
    Maiores voluptatum recusandae cupiditate!
  </p>
</body>

</html>